Novel DC Power Conversion Circuit

ABSTRACT

The inventive technology, in certain embodiments, may be generally described as a solar power generation system with a converter, which may potentially include two or more sub-converters, established intermediately of one or more strings of solar panels. Particular embodiments may involve sweet spot operation in order to achieve improvements in efficiency, and bucking of open circuit voltages by the converter in order that more panels may be placed on an individual string or substring, reducing the number of strings required for a given design, and achieving overall system and array manufacture savings.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation application of U.S. Non-Provisionalapplication Ser. No. 16/028,188, filed Jul. 5, 2018, issuing as U.S.Pat. No. 10,714,637 on Jul. 14, 2020, which is a continuationapplication of U.S. Non-Provisional application Ser. No. 15/164,806,filed 25 May 2016, now issued as U.S. Pat. No. 10,032,939, which is acontinuation application of U.S. Non-Provisional application Ser. No.13/503,011, filed 19 Apr. 2012, now issued as U.S. Pat. No. 9,466,737,which is the United States National Phase of international patentapplication number PCT/US2010/053253, filed 19 Oct. 2010, published on28 Apr. 2011 as WO 2011/049985 A1 and which claims priority to U.S.Provisional App. No. 61/253,025, filed 19 Oct. 2009, each saidapplication hereby incorporated herein in its entirety by reference.

TECHNICAL FIELD

This invention relates to methods and apparatus involving grid- orelectrical power network-tied photovoltaic (PV) converters. In oneembodiment, it especially relates to multiple panel grid-tied PVconverters commonly deployed in either commercial or even residentialpower installations.

BACKGROUND

Many common PV converters may have challenges to meet cost andreliability challenges. Such challenges need to be viewed from theperspective of generating their electricity savings for payback ofinitial investment over longer periods. The present invention providessystems that may in some embodiments address cost and reliability goalsfor many PV systems.

At the current time the use of PV (photovoltaic) panels to generateelectricity may be in a period of rapid growth. The cost of solar powermay even be decreasing and many factors appear to limit the growth ofnon-renewable energy sources. Today there are both large scale systemsand small-scale systems being deployed. In a typical system, many PVpanels may be connected to a grid-tied converter or inverter which maytake the power from the PV panels, perhaps at or near their maximumpower points, and may then transforms it to AC power suitable toback-feeding the grid or other electrical power network.

SUMMARY OF THE INVENTION

This invention solves one fundamental disadvantage of string converterswhen compared to module level converters. In solar PV installationsthere are various architectures which address the need for allowingsolar PV modules to operate at their

Maximum Power Point (MPP). Conventional central inverters 1 operate withtheir input voltage controlled to find the MPP of an array. This arraytypically has several (to hundreds or thousands) of strings 2 ofindividual solar modules 3. But every module has an individual MPP andan array MPP solution leaves energy unharvested. At the other end of thespectrum MPP per module converters allow maximum harvesting from eachmodule.

There is a middle ground being considered today whereby each string isequipped with a DC/DC converter operating at the MPP for a series stringof PV modules 5.

For certain modules (e.g., thin film modules), the ratio of V_(OC) coldto V_(MPP) hot may be 2:1. Take for example a module having V_(OC)cold=70 volts and hot=35 volts. In this installation the rail voltage ona cold day when the inverter is not connected to the grid will be70×8=560 volts. This is safely below the US regulatory limit of 600volts. A conventional string converter could simply be connected to thisstring. Obviously it would not meet the same regulatory limit with aconventional system if more modules were added to this string.

The normal operating voltage of this string though may be only 35×8=280volts. This low operating voltage requires a large wire plus theinverter must operate at 280 volts while being able to withstand 560volts. The circuit of an embodiment of this invention capitalizes on thesituation where thin film solar PV modules typically operate withV_(MPP) of, less than, and perhaps only about half of, V_(OC) cold.

One advantage is that string MPP architectures gain much of the energyof individual module MPP architectures while costing a bit less. Thereare a few limitations of string MPP architectures:

-   -   The harvesting is less compared to MPP/module as current may        vary within a string which cannot be corrected.    -   Diagnostic information is only available at the string level        instead of module level.    -   During periods when the downstream inverter is not able to        deliver power, the string voltage moves to the open circuit        voltage of each module added together. This limits the number of        modules which may be connected in a string for a given        regulatory voltage level.    -   The string inverter must operate over a wide input voltage        range.

A novel string DC/DC converter with MPP can be used to solve the thirdlimitation while adding several new benefits. Solving thismodules-per-string problem allows a solar PV system designer to placemore modules per string (perhaps 2× more), resulting in fewer stringsand fewer combiner boxes. The final result can be a lowering of BalanceOf System (BOS) cost. As will be seen the architecture disclosed alsoallows a DC/DC converter to operate at its sweet spot improvingefficiency. Another aspect of this invention is the suitability of thisarchitecture for thin film photovoltaic modules in that it can addressthe low fill factor of thin film technologies with a low cost, highlyefficient design.

One advantage of the inventive technology may be, in embodiments, theability to place more modules on a string, thereby lowering the totalnumber of strings that a solar array must have to generate a designpower. Such reduction of the total number of strings translates into acost savings, as strings often require expensive componentry (e.g.,combiner boxes). In some embodiments, twice as many solar panels may beplaced on a string, relative to conventional technologies.

Additional Exemplary Advantages: Because of the allowed regulatory upperlimit voltage (recall that even during an open circuit, during sunlighthours, where no power is output from the DC-AC inverter, there is avoltage output), and because of the fact that typically, an open circuitvoltage from a solar panel is greater than a loaded (e.g., operatingcircuit) voltage from that solar panel (because MPP controls effectiveduring loaded circuit conditions reduce output voltages as compared withopen circuit conditions, in order to achieve maximum power), the numberof solar panels per string in certain prior art string architecture waslimited by the open circuit condition (again, because it produces highervoltages and because compliance with applicable voltage regulations ismandatory), with the inventive technology, the number of modules perstring can be increased. This may be due to the bucking of open circuitvoltages (which are typically higher than operational voltages); in thisway, relative to a conventional apparatus with a maximum number ofpanels in a string, during open circuit condition, more panels can beadded without going over the limit. And during operation, the voltagesum of the loaded panels of a single string can be greater than itotherwise would be (which is beneficial because such means more powerper string . . . and the associated cost savings). This may be due tothe fact that in embodiments of the inventive technology, the converter,established intermediately within the string, is connected with twoportions of the string in which it is established via conductors, andthe loaded circuit (e.g., MPP) voltages of such conductors sum to besubstantially equal to the output from the converter. Such “sweet spot”operation affords additional efficiency of operation benefits relativeto conventional apparatus. As such, not only does the inventivetechnology, in particular embodiments, offer advantages relative to anincrease in the number of modules per string, but it also offersbenefits relative to the efficiency of operation (due to “sweet spot”operation). Open circuit voltages may be reduced, or bucked, by theconverter, such that they sum to at or below the maximum regulatoryvoltage. Of course, additional advantages may be as disclosed elsewherein this patent application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one type of traditional systemgrid-tied solar power system with an inverter.

FIG. 2 shows a conceptual embodiment of the invention.

FIG. 3 shows one conceptual embodiment of the invention.

FIG. 4 shows a schematic of one embodiment of the invention.

FIG. 5 shows a schematic of one embodiment of the invention, showingloaded circuit voltages (Vcc), or Vmpp (maximum power point), and opencircuit voltages (Voc) of various conductors/components. The voltmeterhookups are shown to illustrate where the Voc of 0V, 600V and the Vccmeasurements of 300V are taken. Here, a maximum output voltage on rail62 is 600V.

FIG. 6 shows a schematic of one embodiment of the invention.

FIG. 7 shows a schematic of one embodiment of an inventive DC-DC powerconverter.

FIG. 8 shows a schematic of one embodiment of an inventive DC-DC powerconverter.

FIG. 9 shows a schematic of one embodiment of an inventive DC-DC powerconverter.

FIG. 10 shows a prior art apparatus.

DESCRIPTION OF PREFERRED EMBODIMENTS

As may be understood from the earlier discussions, the present inventionincludes a variety of aspects, which may be combined in different ways.The following descriptions are provided to list elements and describesome of the embodiments of the present invention. These elements arelisted with initial embodiments, however it should be understood thatthey may be combined in any manner and in any number to createadditional embodiments. The variously described examples and preferredembodiments should not be construed to limit the present invention toonly the explicitly described systems, techniques, and applications.Further, this description should be understood to support and encompassdescriptions and claims of all the various embodiments, systems,techniques, methods, devices, and applications with any number of thedisclosed elements, with each element alone, and also with any and allvarious permutations and combinations of all elements in this or anysubsequent application.

Consider first the architecture and circuit diagram of one embodiment ofthe invention shown in FIG. 4. This circuit has two of the formerstrings 5 combined into a power converter 52 and having a series diode72, all making up a new string 60. The power converter can have acontrolled intra-string connector 9, and in a preferred embodiment, twoDC/DC converters 55 (the upper box and the lower box; subconverters 52)perhaps appearing to operate in a mirror image of each other, amongother options. During periods of no load, when the downstream inverteris not connected to the grid, each of the DC/DC subconverters mayoperate in buck mode and reduce the string input voltage perhaps byabout one half. At this time, for example, each DC/DC subconverter 55may have a Voc input as high as 560 volts but an output of 280 volts.One may see that even though twice as many modules are connected in thisstring, the output voltage may remain at 560 volts, even when theindividual modules are operating at Voc. There is little efficiencypenalty for the DC/DC inverter at this time as there is no power beingprocessed.

During power generating periods (loaded circuit condition), whenindividual module outputs may drop to VMPP, (the series of eight modulesmaking perhaps ˜280 volts) the DC/DC subconverter 55 may now pass theinput voltage relatively unaltered to the output which may remain at 560volts (conservatively below an upper maximum allowed by regulation of600V). Importantly at this time when the DC/DC subconverters 55 areoperating at significant power, they are also at their sweetspot—neither boosting nor bucking significantly and therefore operate attheir highest efficiency!

The DC/DC subconverters 55 may be simply buck mode converters or may bemany differing types of converters. This disclosure does not intend tolimit aspects of the actual power converter or other element that may beused. For example, as shown conceptually in FIG. 3, embodiments mayinclude: a circuit which divides voltage 308, a coupled inductorcircuit, a simple switch perhaps across one or more DC/DC subconverters,a circuit having switching capability 309, an intra-string controlelement 310, a controllable intra-string connection 9, other designs forDC/DC converters, various circuits which may or may not includeMPP/string capabilities, or even any circuit which apportions voltagesbetween strings. Various embodiments may result in different operatingconditions and/or operational ranges. One preferred embodiment may bedual mode converters perhaps such as shown in FIG. 4. For a detailedcircuit operation for an embodiment of a dual mode DC/DC converter onemay refer to PCT publication number WO2009051853 and U.S. Pat. No.7,605,498. These converters may or may not include P & O MPP trackingfor the string—even more, this circuit could provide MPP tracking foreach half string, extremely high efficiency, and programmable voltageand current limits.

As a result the circuit and architecture of embodiments of the inventionmay provide the following benefits:

-   -   Substantially more modules may be included in a string—reducing        BOS cost. In the example of FIG. 3, there are twice as many        modules in a string.    -   This circuit may provide MPP tracking for each half string        improving harvesting or conventional string converters.    -   This circuit can greatly simplify a downstream inverter by        providing constant or a narrow range of operating voltage for        the inverter.    -   This circuit may operate at the highest possible efficiency by        typically operating with input voltage near output voltage for        each DC/DC converter.    -   This circuit may make use of extremely high efficiency        converters, perhaps as described in PCT publication number        WO2009051853 and U.S. Pat. No. 7,605,498.    -   While individual modules operate at VMPP, the string output and        the array may operate at much higher voltage limited only by the        regulatory environment.    -   This circuit simultaneously operates at a high efficiency while        delivering power at the highest allowable string voltage.    -   There is no point in the array which exceeds the regulatory        voltage limit.

The inventive technology, in embodiments, may adjust loaded conditionpower per string or even per substring (string portion 50) to achievemaximum power point for that string or substring, while bucking opencircuit voltages. Indeed, in particular embodiments, the purpose of theconverter may be, at least in part, to extract, perhaps using switches(e.g., perhaps one for each string or substring), maximum power from thestring or substrings with which it is connected, while bucking opencircuit voltages to provide for a greater number of panels for eachstring (or substring). While the converters disclosed herein may be, attimes, presented in the context of solar array power generation, theymay have other applications.

In particular embodiments of the inventive technology, a DC-DC converter52 may be established intermediately within a string of solar panels(which includes but is not limited to directly in the center of). Whilein certain embodiments a converter so established may be establishedsuch that the number of solar panel(s) serially connected between theconverter and the lower rail is the same as the number of panelsserially connected between the converter and the upper rail, such asymmetric architecture is not a necessary feature.

Particular embodiments may involve operation of the converter at a“sweet spot”, where the sum of the voltages of conductors from stringportions to the converter is substantially equal to (e.g., within 20%of) the voltage of the conductor leading to the upper (or positive) rail(voltages measured relative to a lower or negative rail; see FIG. 5).Operational efficiencies inhere in “sweet spot” operation; indeed, asbut one example, a converter that takes an input of 300 volts andoutputs 600 volts is less efficient than a converter that, operating atits “sweet spot”, takes an input of 600 volts and outputs 600 volts (orsubstantially 600 volts, wherein 600 volts is the allowable limit, alsoexpressed as the maximum regulatory voltage) (see, e.g., FIG. 5). Inparticular embodiments, the output from the converter may be at or closeto (e.g., slightly below, or conservatively below), a regulatory limit.

Relatedly, the inventive technology, in particular embodiments, may beviewed as power architecture that allows a substantially constantvoltage applied to a positive rail during open circuit and loadedcircuit conditions (i.e., where the open circuit voltage of the positiverail relative to the negative rail is substantially equal to the loadedcircuit voltage of the positive rail relative to the negative rail),and/or that affords the efficiency benefits of sweet spot converteroperation while perhaps also outputting a near maximum regulatoryvoltage (see, e.g., FIG. 5). It should be understood that particularfeatures of certain embodiments of the inventive technology may not becritical to, and may not be found in, all embodiments. For example,“sweet spot” operation might not be found in all types of convertersused in the inventive technology.

In particular embodiments, the intermediately connected DC-DC convertermay include sub-converters 55. Where two sub-converters are present, afirst string portion may be electrically connected with onesub-converter and a second string portion may be electrically connectedwith the other sub-converter. The subconverters may be connected with anintra-string connector 9. The converter, regardless of whether itincludes sub-converters, may be a buck/boost converter (e.g., a dualmode conductor as described in PCT publication number WO2009051853 andU.S. Pat. No. 7,605,498). Indeed the sub-converters themselves may be“dual mode” type as these references describe.

In particular embodiments where an intermediately established converterdivides a solar panel string into two portions, the two string portionsmay operate as if in parallel during an open circuit condition andoperate in as if in series during a closed (operating, e.g., MPP)circuit condition. Further, in particular embodiments, convertercircuitry (e.g., switching circuitry), may be able to smoothlytransition from series connected substrings (string portions) toparallely connected substrings.

It should be understood that while the exemplary disclosure (e.g., inwriting and/or figures) may appear to relate most particularly tounipolar designs, this application is intended to, and in fact does,also disclose bipolar designs (e.g., where the negative, or lower railhas a voltage of zero).

At least one embodiment of the inventive technology may be generallydescribed as a solar power system that includes: at least two solarpanels 56 of a first solar power string 60; a first DC-DC converter 52connected within the first solar power string; a negative rail 64electrically connected with one of the at least two solar panels and thefirst DC-DC converter; a positive rail 62 electrically connected with adifferent one of the at least two solar panels and the first DC-DCconverter; and a DC-AC power inverter 63 that acts on power conducted bythe negative and positive rails. Often, a rail receives a plurality ofinputs from parallely disposed components.

In particular embodiments the first DC-DC converter may operate at asweet spot during loaded circuit condition of the system. Moreparticularly, the first DC-DC converter connected within the first solarpower string may be connected with a first portion 67 of the first solarpower string through a first string portion conductor 68 and connectedwith a second portion 65 of the first solar power string through asecond string portion conductor 66, where the second string portionconductor may have a second string portion loaded circuit voltage value(e.g., 600V, including slightly less than 600V) relative to the negativerail, the first string portion conductor may have a first string portionloaded circuit voltage value (e.g., 300V) relative to the negative rail,and a sum of the first string portion loaded circuit voltage value andthe second string portion loaded circuit voltage value may besubstantially equal to a loaded circuit voltage value 600V of thepositive rail relative to the negative rail.

In particular embodiments, the system may further comprise a secondsolar power string 70 connected in parallel with the first solar powerstring; and a second DC-DC converter 71 connected may be establishedwithin the second solar power string. A diode 72 may be establishedbetween the positive rail and the converter.

The positive rail may have an open circuit voltage (e.g., 600V) relativeto the negative rail and a loaded circuit voltage relative to thenegative rail that are substantially equal. The positive rail may have aloaded circuit voltage relative to the negative rail that isconservatively close (such that expected variations in operatingconditions will not cause an excessive voltage) to a regulatory maximumvoltage limit (e.g., 560V).

In particular embodiments, the first DC-DC converter may include twosub-converters 55. At least one of the two sub-converters may be a dualmode converter; at least one of the two sub-converters may be a buckconverter; and/or at least one of the two sub-converters may be aconverter that is neither dual mode, buck, nor boost. Typically, astrictly boost converter would not be applicable, as there may be noneed for boosting in converters of certain embodiments of the invention.

It is of note that in certain embodiments, the negative rail (where therail can have either a negative or zero voltage value), is a lower rail,and the positive rail is an upper rail.

Further, the power system can be unipolar or bipolar.

At least one embodiment of the inventive technology may be generallydescribed as a solar power system comprising a string of solar panels60; a DC-DC converter 52 intermediately connected within the string as apart of the string; a positive rail 62 and a negative rail 64 with whicheach the string and the DC-DC converter is connected; and at least oneDC-AC power inverter 63 that acts on DC power conducted by the positiveand negative rails.

In particular embodiments, the first DC-DC converter may operate at asweet spot during loaded circuit condition of the system. Moreparticularly, the first DC-DC converter connected within the string maybe connected with a first portion of the string through a first stringportion conductor and connected with a second portion of the stringthrough a second string portion conductor, where the first stringportion conductor has a first string portion loaded circuit voltagevalue relative to the negative rail, the second string portion conductorhas a second string portion loaded circuit voltage value relative to thenegative rail, and a sum of the first string portion loaded circuitvoltage value and the second string portion loaded circuit voltage valueis substantially equal to a loaded circuit voltage value of the positiverail relative to the negative rail.

The string may be a first string, and the system may further comprise atleast one additional string 70 of solar panels connected in parallelwith the first string. The system may further comprise at least oneadditional DC-DC converter 71, each of which may be connected within oneof the at least one additional string of solar panels.

A diode may be established between the DC-DC converter and the positiverail 62. The positive rail may have an open circuit voltage relative tothe negative rail 64 and a loaded circuit voltage relative to thenegative rail that are substantially equal; further, or instead, thepositive rail may have a loaded circuit voltage relative to the negativerail that is equal to or slightly less than a regulatory voltage limit(e.g., a federally imposed limit of 600 V).

In particular embodiments, the DC-DC converter may comprise twosub-converters (e.g., at least one of which is a dual mode converter(see WO2009/051853, and U.S. Pat. No. 7,605,498), at least one of whichis a buck converter, and/or at least one of which is neither a dual modenor buck converter. In particular embodiments, the system may beunipolar or bipolar. Further, the positive rail may be an upper rail andthe negative rail may be a lower rail.

At least one embodiment of the inventive technology may be described asa solar power system comprising a string 60 of solar panels; a DC-DCconverter 52 established intermediately within the first string of solarpanels, the converter dividing the string into a first portion 67 and asecond portion 65, the first portion connected with the DC-DC converterthrough a first string portion conductor 68 and the second portionconnected with the DC-DC converter through a second string portionconductor 66; a negative rail 64 connected with the second stringportion and the DC-DC converter; a positive rail 62 connected with thefirst string portion and the DC-DC converter, and a converter conductor80 traveling from the converter towards the positive rail 62. In certainembodiments: a loaded circuit voltage of the first string portionconductor relative to a voltage of the negative rail has a first stringportion loaded circuit voltage value; a loaded circuit voltage of thesecond string portion conductor relative to a voltage of the negativerail has a second string portion loaded circuit voltage value; a loadedcircuit voltage of the positive rail relative to the negative rail has apositive rail loaded circuit voltage value; an open circuit voltage ofthe positive rail relative to the negative rail has a positive rail opencircuit voltage value; a loaded circuit voltage of the converterconductor relative to the negative rail has a converter conductor loadedcircuit voltage value; and a sum of the first string portion loadedcircuit voltage value and the second string portion loaded circuitvoltage value is substantially equal to the converter conductor loadedcircuit voltage value. Such may be sweet spot operation, and operatingto achieve such condition is sweet spot operating.

The positive rail loaded circuit voltage value may be substantiallyequal to the positive rail open circuit voltage value, and/or a sum ofthe first string portion loaded circuit voltage value and the secondstring portion loaded circuit voltage value is substantially equal tothe positive rail loaded circuit voltage value. This condition may beseen during sweet spot operation.

An open circuit voltage of the first string portion conductor relativeto the negative rail may have a first string portion open circuitvoltage value, an open circuit voltage of the second string portionconductor relative to the negative rail may have a second string portionopen circuit voltage value, and an open circuit voltage of the converterconductor relative to the negative rail may have a converter conductoropen circuit voltage value. In certain embodiments, a sum of the firststring portion open circuit voltage value and the second string portionopen circuit voltage value is substantially equal to the converterconductor open circuit voltage value. In certain embodiments, a sum ofthe first string portion open circuit voltage value and the secondstring portion open circuit voltage value is substantially equal to theconverter conductor loaded circuit voltage value. In particularembodiments, a sum of the first string portion open circuit voltagevalue and the second string portion open circuit voltage value is lessthan or equal to a regulatory maximum voltage limit. Relationshipsbetween open circuit voltages as described herein may be the result ofbucking of voltages by the converter (or sub-converters that may beestablished therein).

In particular embodiments, the first string portion loaded circuitvoltage value is equal to the second string portion loaded circuitvoltage. An open circuit voltage of the positive rail relative to thenegative rail may be said to be a positive rail open circuit voltagevalue, and the positive side of the second string portion open circuitvoltage value may be substantially equal to the positive rail opencircuit voltage value. The negative side of the first-string portionopen circuit voltage value may be, in certain embodiments, substantiallyequal to zero. A sum of the first-string portion loaded circuit voltagevalue and the second string portion loaded circuit voltage value issubstantially equal to the positive rail open circuit voltage value. Thepositive rail open circuit voltage value may be substantially equal tothe positive rail loaded circuit voltage value.

In certain embodiments, the converter conductor is a converter outputconductor, and the converter conductor loaded circuit voltage value isconservatively less than a regulatory maximum voltage limit. Further,the converter may include two sub-converters, at least one of which is adual mode converter; at least one of which may include a buck converter;and at least one of which is neither dual mode, buck, nor boost.Additionally, the negative rail may be a lower rail, and the positiverail may be an upper rail. As with other designs, the power system isunipolar or bipolar.

At least one embodiment of the inventive technology may be described asa solar power control method comprising the steps of generating powerfrom at least two solar panel substrings of a solar power string that isconnected to negative and positive rails; maximum power pointcontrolling, with a maximum power point controller, a voltage output byeach the at least two solar panel substrings; and converting a power atmaximum power point to AC. The step of maximum power point controllingmay comprise the step of controlling with a maximum power pointcontroller having at least two switches. Such switches may provideshunting functionality. The step of maximum power point controlling,with a maximum power point controller, a voltage output by each the atleast two solar panel substrings may comprise the step of maximum powerpoint controlling, with DC-DC converter.

At least one embodiment of the inventive technology may be described asa solar power control method comprising the steps of generating powerfrom two solar panel substrings of a solar panel string that isconnected to negative and positive rails; and mirror image controllingthe power from two solar panel substrings of a converter establishedwithin the solar power string. Mirror image controlling may involvesymmetric identical control where inputs are equal. The step of mirrorimage controlling the power from the two solar panel substrings maycomprise the step of maximum power point controlling. It may involve thestep of controlling with two sub-converters that each comprise a switch;such sub-converters may be substantially identical, but perhaps orientedin mirror image fashion, perhaps with any diodes changed from a strictmirror image so as to enable proper functionality as intended.

At least one embodiment of the inventive technology is a solar powercontrol method comprising the steps of: bucking open circuit voltagefrom each of a plurality of solar panel substrings of a solar panelstring of a solar power system, with a converter during open circuitcondition; and sweet spot processing loaded circuit voltage from each ofthe plurality of solar panel substrings during loaded circuit condition.The method may further comprise the step of pulling maximum power pointpower from the each of the plurality of solar panel substrings duringloaded circuit condition. A sum of voltages associated with the maximumpower point power of each of the plurality of solar panel substrings maybe less than or equal to a maximum regulatory voltage. The step ofbucking open circuit voltage from each of a plurality of solar panelsubstrings may comprise the step of bucking so that a sum of buckedvoltages is less than or equal to a maximum regulatory voltage; the stepof bucking open circuit voltage from each of a plurality of solar panelsubstrings comprises the step of bucking open circuit voltage toapproximately one-half voltage input to the converter by each of thesubstrings.

At least one embodiment of the inventive technology may be described asa solar power control system comprising: at least two solar panelsubstrings of a solar panel string of a solar power system; a controllerestablished so as to maintain an open circuit voltage from thecontroller during an open circuit condition of the solar power systemthat is substantially equal to a loaded circuit voltage from thecontroller during a loaded circuit condition of the solar power system.In certain embodiments, an average of the open circuit voltage and theloaded circuit voltage is substantially equal to a maximum regulatoryvoltage.

At least one additional embodiment of the inventive technology may bedescribed as a solar power control method comprising the steps of:loaded circuit, high efficiency, high power delivering of powergenerated by a solar panel string; and converting the delivered power toAC. The step of loaded circuit, high efficiency, high power deliveringof power generated by a solar panel string comprises the step of loadedcircuit, high efficiency, high power delivering of power generated by atleast two solar panel substrings of the solar panel string. The step ofloaded circuit, high efficiency, high power delivering of powergenerated by a solar panel string may comprise the step of neitherbucking nor boosting (or simply not comprise the step of bucking orboosting, or comprise the step of refraining from bucking or boosting).The step of loaded circuit, high efficiency, high power delivering ofpower comprises the step of delivering maximum power point power.

It is of note that during “sweet spot” operation, where a converter hassub-converters, the inputs to and the outputs from each of thesub-converters is also substantially the same.

At least one embodiment of the inventive technology may be described asa solar power string control method, comprising the steps of generatingpower with solar panels of at least two substrings of a solar powerstring; managing circuit functionality with a DC-DC converterestablished intermediately of said string, said power controllerdefining said substrings (e.g., by dividing a larger string connectedbetween rails into two substrings). The step of managing circuitfunctionality may comprise the steps of bucking open circuit voltagesgenerated by said substrings, and, perhaps also the step of sweet spotoperating during loaded circuit condition. Such converter may alsoachieve MPP control (e.g., with switches of said converter).

While novel converters disclosed herein may be, at times, presented inthe context of solar array power generation, they may have otherapplications. FIGS. 7, 8 and 9 show examples of novel converters thatmay find application as DC-DC converters for MPP control of panelstrings or substrings.

As shown in FIG. 8, a DC-DC power converter 101 may comprise: a switch102 along a first conductor 103 that is established between two nodes,the two nodes including a first 104 node defined by an intersection ofthe first conductor, a second conductor 105, a third conductor 106 and afourth conductor 107, and a second node 108 defined by an intersectionof the first conductor with a fifth conductor 109, a sixth conductor 110and a seventh conductor 111; a first diode 112 established along thesecond conductor between a third node 113 and the first node, the thirdnode defined by an intersection of the second conductor, the fifthconductor, and a lower voltage conductor 114 that electrically connectsthe converter, the first diode allowing flow towards the first node; asecond diode 115 established along the third conductor between the firstnode and a fourth node 116, the fourth node defined by an intersectionof the third conductor, the sixth conductor, and a higher voltageconductor 117 that electrically connects the converter, the second diodeallowing flow towards the fourth node; a third diode 118 establishedalong the fifth conductor between the third node and the second node,the third diode allowing flow towards the second node; a fourth diode119 established along the sixth conductor between the second node andthe fourth node, the fourth diode allowing flow towards the fourth node;a first inductor 120 established along the fourth conductor; and asecond inductor 121 established along the seventh conductor.

In particular embodiments, the system may further comprise a first powergenerator 198 electrically connected with the first inductor. The firstpower generator may be a first solar panel substring; current from thefirst solar panel substring may flow away from the first node. The firstpower generator may be electrically connected with the high voltageconductor. The system may further comprise a second power generator 199electrically connected with the second inductor; the second powergenerator may be a second solar panel substring. Current from the secondsolar panel substring may flow towards the second node. Further, thesecond power generator may be electrically connected with the lowvoltage conductor. The system may further comprise at least oneadditional parallely connected converter 200 and additional powergenerators 201 associated with (e.g., connected with) each of the atleast one additional parallely connected converter. In certainembodiments, the higher voltage conductor connects to a positive rail62, and the first power generator is connected with the positive rail.In certain embodiments, the lower voltage conductor connects to anegative rail 64 and the second power generator is connected with thenegative rail. Further, the DC-DC converter may be established within asolar panel string, the DC-DC converter may be part of a unipolar powergeneration system; and/or the DC-DC converter may be part of a bipolarpower generation system.

As shown in FIG. 9, at least one embodiment of the inventive technologymay be a DC-DC converter 130 that comprises: an inductor 131 establishedalong a first conductor 132, between a first 133 and a second node 134,the first node defined by an intersection of the first conductor, asecond conductor 135, and a third conductor 136, and the second nodedefined by an intersection of the first conductor, and a fourth 137 andfifth conductor 138; a first switch 139 established along the secondconductor between the first node and a third node 140, the third nodedefined by an intersection of the second conductor, a sixth conductor141, and a first power generator connector 142; a diode 143 establishedalong the third conductor between the first node and a fifth node 144defined by an intersection of the third conductor, the sixth conductor,and a higher voltage conductor 145, the diode allowing flow towards thefifth node; a capacitor 146 established along the sixth conductorbetween the third node and the fifth node; a second switch 147established along the fourth conductor between the second node and afourth node 148, the fourth node defined by an intersection of thefourth conductor, a seventh conductor 149, and a second power generatorconnector 150; a diode 151 established along the fifth conductor betweena sixth node 152 and the second node, the sixth node defined by anintersection of the fifth conductor, the seventh conductor, and a lowervoltage conductor 153, the diode allowing flow towards the second node;and a capacitor 154 established along the seventh conductor between thefourth node and the sixth node.

In certain embodiments, the system may include a first power generator198 connected to the first power generator connector; current may flowfrom the first power generator away from the DC-DC converter. The systemmay further comprise a second power generator 199 connected to thesecond power generator connector; current may from from the second powergenerator towards the DC-DC converter. The system may further compriseat least one additional parallely connected converter 200 and at leasttwo additional power generators 201 connected with each of the at leastone additional parallely connected converter. The converter may be partof a unipolar power generation system or a bipolar power generationsystem. In certain embodiments, the higher voltage conductor connects toa positive rail 62, as may be the first power generator. The lowervoltage conductor may connect to a negative rail 64, as may be secondpower generator.

As shown in FIG. 7, at least one additional embodiment of the inventivetechnology may be a DC-DC converter 170 comprising: an inductor 171established along a first conductor 172 between a first node 173 and asecond node 174, the first node defined by an intersection of the firstconductor, a second conductor 175, a third conductor 176, and a fourthconductor 177, the second node defined by an intersection of the firstconductor, a fifth conductor 178, a sixth conductor 179, and a seventhconductor 180; a first diode 181 established along the third conductorbetween the first node and a third node, the third node 182 defined byan intersection of the third conductor, the fifth conductor, an eighthconductor 183 and a higher voltage conductor 184, the first diodeallowing flow towards the third node; a first switch 185 establishedalong the fifth conductor between the second node and the third node; asecond switch 186 established along the fourth conductor between thefirst node and a fourth node 187, the fourth node defined by anintersection of the fourth conductor, the eighth conductor, and a firstpower generator connector 188; a first capacitor 189 established alongthe eighth conductor between the third node and the fourth node; asecond diode established along the sixth conductor between the secondnode and a fifth node 190, the fifth node defined by an intersection ofthe sixth conductor, a ninth conductor 191, the second conductor, and alower voltage conductor 192, the second diode allowing flow towards thesecond node; a third switch 193 established along the second conductorbetween the first node and the fifth node; a fourth switch 194established along the seventh conductor between the second node and asixth node 195, the sixth node defined by an intersection of the seventhconductor, the ninth conductor, and a second power generator connector196; and a second capacitor 197 established along the ninth conductorbetween the fifth node and the sixth node. In particular embodiments,the DC-DC converter may be part of a unipolar power generation system ora bipolar power generation system. The first power generator 198 may beconnected to the first power generator connector and the higher voltageconductor; current may flow from the first power generator away from theconverter. The apparatus may further comprise a second power generator199 connected to the second power generator connector and the lowervoltage conductor. Current may flow from the second power generatortowards the converter. The apparatus may further comprise at least oneadditional parallely connected converter 200 and additional powergenerators 201.

In the various descriptions provided herein, the following may apply:conductor can be one or more than one wire (it may be whateverconducts). Substantially equal may mean within less than or equal to20%, 17.5%, 15%, 12.5%, 10%, 7.5%, 5%, or 2.5%. Two components orconductors may be electrically connected even if they are intervening(typically non-converting) devices. Diodes may be optional; indeed somecapacitors, particularly in the figures of the various inventiveconverters, may not even be shown. The term negative rail applies wherethere is a rail type conductor that is either at negative (e.g., thenegative of the positive voltage of the positive rail) or zero volts(negative voltage may be found, e.g., in the case of a bipolar design).It is of note that the inventive converters need not necessarily havepower generation connectors as claimed or described, or power generatorsattached thereto as claimed or described.

As can be easily understood from the foregoing, the basic concepts ofthe present invention may be embodied in a variety of ways. It involvesboth control techniques as well as devices to accomplish the appropriatecontrolling. In this application, the control techniques are disclosedas part of the results shown to be achieved by the various devicesdescribed and as steps which are inherent to utilization. They aresimply the natural result of utilizing the devices as intended anddescribed. In addition, while some devices are disclosed, it should beunderstood that these not only accomplish certain methods but also canbe varied in a number of ways. Importantly, as to all of the foregoing,all of these facets should be understood to be encompassed by thisdisclosure.

The discussion included in this application is intended to serve as abasic description. The reader should be aware that the specificdiscussion may not explicitly describe all embodiments possible; manyalternatives are implicit. It also may not fully explain the genericnature of the invention and may not explicitly show how each feature orelement can actually be representative of a broader function or of agreat variety of alternative or equivalent elements. Again, these areimplicitly included in this disclosure. Where the invention is describedin device-oriented terminology, each element of the device implicitlyperforms a function. Apparatus claims may not only be included for thedevice described, but also method or process claims may be included toaddress the functions the invention and each element performs. Neitherthe description nor the terminology is intended to limit the scope ofthe claims that will be included in any subsequent patent application.

It should also be understood that a variety of changes may be madewithout departing from the essence of the invention. Such changes arealso implicitly included in the description. They still fall within thescope of this invention. A broad disclosure encompassing both theexplicit embodiment(s) shown, the great variety of implicit alternativeembodiments, and the broad methods or processes and the like areencompassed by this disclosure and may be relied upon when drafting theclaims for any subsequent patent application. It should be understoodthat such language changes and broader or more detailed claiming may beaccomplished at a later date (such as by any required deadline) or inthe event the applicant subsequently seeks a patent filing based on thisfiling. With this understanding, the reader should be aware that thisdisclosure is to be understood to support any subsequently filed patentapplication that may seek examination of as broad a base of claims asdeemed within the applicant's right and may be designed to yield apatent covering numerous aspects of the invention both independently andas an overall system.

Further, each of the various elements of the invention and claims mayalso be achieved in a variety of manners. Additionally, when used orimplied, an element is to be understood as encompassing individual aswell as plural structures that may or may not be physically connected.This disclosure should be understood to encompass each such variation,be it a variation of an embodiment of any apparatus embodiment, a methodor process embodiment, or even merely a variation of any element ofthese. Particularly, it should be understood that as the disclosurerelates to elements of the invention, the words for each element may beexpressed by equivalent apparatus terms or method terms—even if only thefunction or result is the same. Such equivalent, broader, or even moregeneric terms should be considered to be encompassed in the descriptionof each element or action. Such terms can be substituted where desiredto make explicit the implicitly broad coverage to which this inventionis entitled. As but one example, it should be understood that allactions may be expressed as a means for taking that action or as anelement which causes that action. Similarly, each physical elementdisclosed should be understood to encompass a disclosure of the actionwhich that physical element facilitates. Regarding this last aspect, asbut one example, the disclosure of a “converter” should be understood toencompass disclosure of the act of “converting”—whether explicitlydiscussed or not—and, conversely, were there effectively disclosure ofthe act of “converting”, such a disclosure should be understood toencompass disclosure of a “converter” and even a “means for converting”.Such changes and alternative terms are to be understood to be explicitlyincluded in the description.

Any acts of law, statutes, regulations, or rules mentioned in thisapplication for patent; or patents, publications, or other referencesmentioned in this application for patent are hereby incorporated byreference. Any priority case(s) claimed by this application is herebyappended and hereby incorporated by reference.

Thus, the applicant(s) should be understood to have support to claim andmake a statement of invention to at least: i) each of the solar powerdevices as herein disclosed and described, ii) the related methodsdisclosed and described, iii) similar, equivalent, and even implicitvariations of each of these devices and methods, iv) those alternativedesigns which accomplish each of the functions shown as are disclosedand described, v) those alternative designs and methods which accomplisheach of the functions shown as are implicit to accomplish that which isdisclosed and described, vi) each feature, component, and step shown asseparate and independent inventions, vii) the applications enhanced bythe various systems or components disclosed, viii) the resultingproducts produced by such systems or components, ix) each system,method, and element shown or described as now applied to any specificfield or devices mentioned, x) methods and apparatuses substantially asdescribed hereinbefore and with reference to any of the accompanyingexamples, xi) the various combinations and permutations of each of theelements disclosed, xii) each potentially dependent claim or concept asa dependency on each and every one of the independent claims or conceptspresented, and xiii) all inventions described herein. In addition and asto computer aspects and each aspect amenable to programming or otherelectronic automation, the applicant(s) should be understood to havesupport to claim and make a statement of invention to at least: xiv)processes performed with the aid of or on a computer as describedthroughout the above discussion, xv) a programmable apparatus asdescribed throughout the above discussion, xvi) a computer readablememory encoded with data to direct a computer comprising means orelements which function as described throughout the above discussion,xvii) a computer configured as herein disclosed and described, xviii)individual or combined subroutines and programs as herein disclosed anddescribed, xix) the related methods disclosed and described, xx)similar, equivalent, and even implicit variations of each of thesesystems and methods, xxi) those alternative designs which accomplisheach of the functions shown as are disclosed and described, xxii) thosealternative designs and methods which accomplish each of the functionsshown as are implicit to accomplish that which is disclosed anddescribed, xxiii) each feature, component, and step shown as separateand independent inventions, and xxiv) the various combinations andpermutations of each of the above.

It should be understood that if or when broader claims are presented,such may require that any relevant prior art that may have beenconsidered at any prior time may need to be re-visited since it ispossible that to the extent any amendments, claim language, or argumentspresented in this or any subsequent application are considered as madeto avoid such prior art, such reasons may be eliminated by laterpresented claims or the like. In drafting any claims at any time whetherin this application or in any subsequent application, it should also beunderstood that the applicant has intended to capture as full and broada scope of coverage as legally available. To the extent thatinsubstantial substitutes are made, to the extent that the applicant didnot in fact draft any claim so as to literally encompass any particularembodiment, and to the extent otherwise applicable, the applicant shouldnot be understood to have in any way intended to or actuallyrelinquished such coverage as the applicant simply may not have beenable to anticipate all eventualities;

one skilled in the art, should not be reasonably expected to havedrafted a claim that would have literally encompassed such alternativeembodiments.

Further, if or when used, the use of the transitional phrase“comprising” is used to maintain the “open-end” claims herein, accordingto traditional claim interpretation. Thus, unless the context requiresotherwise, it should be understood that the term “comprise” orvariations such as “comprises” or “comprising”, are intended to implythe inclusion of a stated element or step or group of elements or stepsbut not the exclusion of any other element or step or group of elementsor steps. Such terms should be interpreted in their most expansive formso as to afford the applicant the broadest coverage legally permissible.As one clarifying example, if a claim were dependent “on claim 20 or anyother claim” or the like, it could be re-drafted as dependent on claim1, claim 15, or even claim 715 (if such were to exist) if desired andstill fall with the disclosure. It should be understood that this phrasealso provides support for any combination of elements in the claims andeven incorporates any desired proper antecedent basis for certain claimcombinations such as with combinations of method, apparatus, process,and the like claims.

1. (canceled)
 2. A solar power system comprising: a DC-DC converterconnected within and as part of a solar power string; a firstunconverted string portion and a second unconverted string portion ofsaid string, said portions separated by, and each connected with, saidDC-DC converter; a first pair of electrical connections connecting saidDC-DC converter across said first unconverted string portion; a secondpair of electrical connections connecting said DC-DC converter acrosssaid second unconverted string portion; a positive rail electricallyconnected with one solar panel of said first unconverted string portionand with said DC-DC converter; and a negative rail electricallyconnected with one solar panel of said second unconverted string portionand with said DC-DC converter.
 3. A solar power system as described inclaim 2 wherein said DC-DC converter is operable at a sweet spot duringloaded circuit condition of said system.
 4. A solar power system asdescribed in claim 2 wherein said DC-DC converter connected within saidsolar power string is connected with said first unconverted stringportion through a first string portion conductor and connected with saidsecond unconverted string portion through a second string portionconductor, wherein said first string portion conductor has a firststring portion loaded circuit voltage value relative to said negativerail, said second string portion conductor has a second string portionloaded circuit voltage value relative to said negative rail, and a sumof said first string portion loaded circuit voltage value and saidsecond string portion loaded circuit voltage value is substantiallyequal to a loaded circuit voltage value of said positive rail relativeto said negative rail.
 5. A solar power system as described in claim 4wherein said string portion loaded circuit voltage values are achievedby bucking by said DC-DC converter.
 6. A solar power system as describedin claim 2 wherein said solar power string is a first solar power stringand further comprising a second solar power string connected in parallelwith said first solar power string.
 7. A solar power system as describedin claim 6 wherein said DC-DC converter is a first DC-DC converter, andfurther comprising a second DC-DC converter connected with said secondsolar power string.
 8. A solar power system as described in claim 2further comprising a diode established between said DC-DC converter andsaid positive rail.
 9. A solar power system as described in claim 2wherein said positive rail is capable of carrying an open circuitvoltage relative to said negative rail and a loaded circuit voltagerelative to said negative rail that are substantially equal.
 10. A solarpower system as described in claim 2 wherein said positive rail iscapable of carrying a loaded circuit voltage relative to said negativerail that is within 7% of a regulatory maximum voltage limit.
 11. Asolar power system as described in claim 2 wherein said DC-DC convertercomprises two sub-converters.
 12. A solar power system as described inclaim 11 wherein at least one of said two sub-converters comprises adual mode converter.
 13. A solar power system as described in claim 11wherein at least one of said two sub-converters comprises a buckconverter.
 14. A solar power system as described in claim 11 whereinsaid two sub-converters share a switch.
 15. A solar power system asdescribed in claim 11 wherein said two sub-converters share an inductor.16. A solar power system as described in claim 2 further comprising aDC-AC power inverter that acts on power conducted by said negative andpositive rails.
 17. A solar power system as described in claim 2 whereinsaid first unconverted string portion comprises a solar panel.
 18. Asolar power system as described in claim 2 wherein said firstunconverted string portion comprises a plurality of solar panels.